1. Field of Invention
The present invention relates to a projection display device in which a light valve, employing, for example, a liquid crystal panel, modulates a light beam from a light source in order to enlarge and project the modulated light beam onto a light projecting surface through a projection lens.
2. Description of Related Art
A projection display device forms modulated light beams in correspondence with image information using liquid crystal light valves in order to enlarge and project the modulated light beams onto, for example, a screen through a projection lens. This type of projection display device is known to produce a high contrast projection image by obliquely illuminating light onto liquid crystal valves which are incident light angle dependent.
A projection display device with a structure in which light obliquely illuminates from a liquid crystal light valve is disclosed in, for example, Japanese Unexamined Patent Publication No. 7-27997. In FIG. 8, the projection display device 1A disclosed in the aforementioned publication comprises a liquid crystal light valve 100A for modulating light emitted from a light source 80A, a projection lens 60A for enlarging and projecting the light modulated by the liquid crystal light valve 100A onto a screen 1000, and a condenser lens 960A disposed adjacent to the light incident surface of the liquid crystal light valve 100A.
In the projection display device 1A, the liquid crystal light valve 100A, the condenser lens 960A, and the projection lens 60A are arranged such that their optical axes 100L, 960L, and 60L are parallel to each other. The light source 80A is mounted such that its optical axis 80L is set obliquely at a predetermined angle from the optical axes 100L, 960L, and 60L of the aforementioned optical elements.
In the projection display device 1A disclosed in Japanese Unexamined Patent Publication No. 7-27997, however, it is necessary to adjust the mounting angle of the light source 80A, which is troublesome to perform. In addition, it is difficult to mount all of the optical elements with high precision, since the condenser lens 960A, the liquid crystal light valve 100A, and the projection lens 60A, must be moved along the optical axis 80L of the light source such that their optical axes 960L, 100L, and 60L arc set parallel to each other.